PROJECT SUMMARY/ABSTRACT The overall goal of this research is to better understand how astrocytes in the medial subnucleus of the central amygdala (CeM) modulate conditioned fear behaviors. We recently found using brain slices that exogenous activation of astrocytes in the CeM powerfully regulates synaptic transmission and decreases CeM neuronal activity. However, critical gaps remain in identifying the role of CeM astrocytes in vivo, their contribution during fear conditioned behaviors, and the neurochemical pathways that couple the concerted activity of neuronal and astrocyte networks in the CeM. The goal of this proposal is therefore to address these gaps in knowledge by performing measurements of astrocytic and neuronal activity in the amygdala in freely, behaving mice using optical and genetic methods. In Aim1 we will record the activity of astrocytes in the CeM during the acquisition, expression and extinction of cued fear conditioned behaviors. They will provide the first physiological evidence that astrocytes are specifically and differentially activated during specific phases of conditioned fear responses. In Aim 2 we will determine whether CeM astrocytes have an endogenous role in modulating amygdala-driven responses. It will also further test the role of astrocytic endocannabinoid signaling in these behaviors. In Aim 3 we will determine the cellular and behavioral consequences upon exogenous activation of CeM astrocytes using chemogenetic and optogenetic methods. In summary, the proposed studies will provide a much more detailed picture on the role of astrocytes in the central amygdala and extend our recent ex vivo amygdala slice studies. This knowledge will pave the way for new pharmacological strategies to treat anxiety/fear disorders, by taking advantage of the uncommon profile of receptor expression of astrocytes to regulate their activity. Therefore, our studies will contribute to generate a new strategy to treat neurological diseases, such as anxiety, post-traumatic stress syndrome by targeting a relatively understudied cell type in the amygdala.